Field of the Invention
The present invention relates to an electrophotographic photosensitive member, a process cartridge including the electrophotographic photosensitive member, and an electrophotographic apparatus including the electrophotographic photosensitive member.
Description of the Related Art
In recent years, organic photoconductive materials (charge generation materials) have been used in electrophotographic photosensitive members that are loaded on process cartridges or electrophotographic apparatuses. The electrophotographic photosensitive member generally includes a support and a photosensitive layer disposed on the support.
The electrophotographic photosensitive member further includes a conductive layer between the support and the photosensitive layer. The conductive layer contains a metal oxide particle for covering defects on the surface of the support.
Japanese Patent Laid-Open No. 2005-234396 describes a technology for reducing image failure due to current leakage caused by addition of a combined metal oxide particle composed of a particle mainly made of a metal oxide and a surface layer mainly made of zinc oxide, to a conductive layer. The term “current leakage” refers to a phenomenon of an excessive current flow in a local portion of an electrophotographic photosensitive member, resulting from occurrence of electric breakdown at the portion.
Japanese Patent Laid-Open No. 2010-224173 describes a technology for reducing residual potential by using a conductive layer containing a titanium oxide particle covered with zinc oxide.
Unfortunately, the results of investigation by the present inventors demonstrated that in the conductive layer containing a metal oxide particle covered with zinc oxide described in the above-mentioned patent documents, application of a high voltage to the conductive layer in a low-temperature and low-humidity environment readily causes current leakage. It was also demonstrated that the above-described conductive layers are still required to reduce the occurrence of variations in dark portion potential and light portion potential during repetitive use. Occurrence of current leakage prevents the electrophotographic photosensitive member from being sufficiently charged and leads to occurrence of image defects, such as a black spot, a horizontal white streak, and a horizontal black streak, on an output image. The term “horizontal white streak” refers to a white streak occurring on an output image in the direction orthogonal to the rotation direction (circumferential direction) of the electrophotographic photosensitive member, whereas the term “horizontal black streak” refers to a black streak occurring on an output image in the direction orthogonal to the rotation direction (circumferential direction) of the electrophotographic photosensitive member.